1. Field of the Invention
This invention relates to thin-film magnetic heads formed by utilizing a thin-film forming process.
2. Description of the Prior Art
Recently, increased efforts have been devoted to increasing the density of recorded information and to minimizing the bulk and size of the recording and reproducing apparatus. Thus increases the desirability of using a thin-film magnetic head of which the magnetic circuit is formed by magnetic thin films thereby advantageously facilitating minimizing bulk and size and reducing space requirements. Particularly when the thin-film magnetic head is in the form of a composite magnetic head (hereinafter called simply "composite head") having two head gaps arranged adjacent to each other in a direction that crosses their recording direction to trace two tracks at a time, the confronting surfaces of the two magnetic circuits can be made extremely small, and the cross talk between the two magnetic circuits can be significantly lessened.
In the following description of this specification, a discussion will be provided of an example of this kind of composite head. FIG. 1 is a perspective view illustrating the known prior art composite head constructed by using thin-film magnetic layers. In FIG. 1, positioned on a lower magnetic layer 2 made of magnetic material are non-magnetic gap members 4a and 4b each made of non-magnetic material, and insulating layers 6a, 6b, 6c and 6d. Upper magnetic layers 8a and 8b are each formed by laminating magnetic thin films. A coil pattern 10 with its two ends 10a and 10b is provided within the thin-film magnetic head comprised of the lower magnetic layer 2 and the upper magnetic layer 8b.
The composite head shown in FIG. 1, besides having small cross talk between the two heads, makes it possible to reduce the thickness as can be seen from the drawing. But, as sectionally illustrated in FIG. 2, the insulating layer 6c is laminated on the coil pattern 10, the upper magnetic layer 8b being further formed on the insulating layer 6c by using the thin-film forming technique. Because the upper magnetic layer 8a, 8b is, therefore, formed on this uneven surface, the electric-magnetic converting characteristic becomes poor, causing the efficiency of the magnetic head to be lowered to a significant extent. In more detail, when the magnetic thin film is applied, the angle of incidence at which the magnetic material spatters with the surface to be coated, becomes very small so that the force of holding the magnetic material in each concave or convex portion reaches levels as high as several tens of Oe. Along with this, therefore, the magnetic resistance increases, and, as a matter of course, the magnetic permeability also is substantially reduced.
Further, upon consideration of the efficiency in structure of the magnetic head, since the head width is about 60 .mu.m, the width of the magnetic path in which the coil pattern 10 is applied (shown by l in FIG. 1), must be about 150 .mu.m. This implies that the maximum possible number of turns of the coil pattern is only a few. Since the necessary number of turns of the coil for the recording and reproducing head is at least twenty, use must be made of an additional transformer or the like. In this case, not only the performance is lowered by the transformer, but also a large space which the transformer occupies must be provided, thereby adversely affecting of the overall product commercialization.